William M. Mihalko

A technique used for soft tissue balancing in knees with valgus deformity is pie-crusting of the lateral soft tissue sleeve. This technique allows the surgeon to direct the lengthening of soft tissue supporting structures according to which areas are taut under tension of the joint space in the operating room.

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  Multiple stabs are made with a scalpel blade parallel to the joint line to effectively elongate the areas of the soft tissue sleeve that are under undue tension. Multiple studies have reported good outcomes in both valgus and varus deformities with this technique ( Figure 13-1 ).

  
  

  
  

  
  

  

  
  
  
  
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  The advantage of pie-crusting, especially on the lateral soft tissue sleeve, is that it leaves a supporting tether that does not allow a larger gap opening on the lateral side of knee in flexion. Cadaver studies have shown that larger releases are not possible with this technique until the lateral collateral ligament is resected. Care is needed when pie-crusting is done in the posterolateral corner because the peroneal nerve is within 1.5 cm. Because the nerve is farther away when the knee is flexed, flexing the knee can help protect the nerve during pie-crusting of the posterolateral corner.

  
  
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  After the distal femur is prepared using the anteroposterior and epicondylar axes as a rotational guide, cut the proximal tibia perpendicular to the mechanical axis and remove osteophytes.

  
  
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  Place the knee in 90 degrees of flexion, and place tensioners medially and laterally between the posterior femoral condyles and proximal tibial cut surfaces. Careful placement of the tensioners is crucial to avoid crushing osteoporotic bone.

  
  
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  Remove any retractors that are causing tension on the affected side, and replace them with rake retractors.

  
  
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  Palpate the soft tissues on the affected side, and release them by pie-crusting until a rectangular flexion gap is achieved.

  
  
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  Place trial components and move the knee into full extension.

  
  
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  If the knee is tight medially or laterally in extension, remove the trial components and reinsert the tensioning devices with the knee in extension.

  
  
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  Repeat pie-crusting with the knee in extension until a rectangular extension gap is achieved.

  
  
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  Replace the trial components, and confirm coronal plane stability in flexion and extension.

  
  
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  Correct any residual discrepancies in the flexion and extension gaps with pie-crusting or, if necessary, standard gap balancing techniques.